DEFECT STABILIZED PERIODIC AMPLITUDE MODULATIONS IN FERROELECTRICS

Theoretical analysis shows that the total free energy of a ferroelectr ic system with free boundary conditions increases with the number of t he inhomogeneous regions, such as domain walls and other modulated str uctures. However, charged defects could lower the total energy of a fe rroelectric system by interacting with charge density fluctuations in inhomogeneous regions. We discuss a special kind of inhomogeneous micr ostructure in a lanthanum doped lead titanate, the amplitude modulatio ns, which can be stabilized by aliovalent dopants.